Notes

Outline

Problem-Solving Techniques Ask questions. Look for things that are familiar. Solve by analogy. Identify the inputs and outputs. Divide and conquer. Use building blocks (new or existing). Merge solutions.

Problem-Solving Case Study Problem: A small company needs an interactive program to figure its weekly payroll. The input data and each employee’s wages should be saved in a secondary storage file, and the total wages for the week should be displayed on the screen so that the payroll clerk can transfer the appropriate amount into the payroll account. Data consists of id, hourly pay rate, and hours worked Regular wage for 40 hours, time and a half after that Store results in a file called payFile Use id 0 to indicate end of data since it is not a valid id

Case Study (continued) Four obvious steps Get the data Compute the results Output data Output total payroll

Main Algorithm Open file payFile, Set total payroll to zero Get Data As long as the employee number is not zero Compute Result Add employee’s wages to the total payroll Output data Get data Output total payroll

Get Data Prompt user for id number Read id number Prompt user for pay rate Read pay rate Prompt user for number hours worked Read number hours worked

Compute Results If hours worked is greater than 40, then Wages = 40 * pay rate + (hours – 40) * 1.5 * pay rate Otherwise Wages = hours * pay rate

Output Data Write id number into payFile Write pay rate into payFile Write hours worked into payFile Write wages into payFile

Output Total Payroll Write total payroll to the screen

Payroll Program //********************************************* // Payroll program // This program computes each employee’s wages and the // total company payroll //********************************************** #include <iostream> #include <fstream> using namespace std; void CalcPay (float, float, float&); const float MAX_HOURS = 40.0; // Maximum normal hours const float OVERTIME = 1.5;   // Overtime pay factor

Payroll Program (continued) int main {   float payRate; // Employee’s pay rat   float hours; // Hours worked   float wages; // Wages earned   float total; // Total company payroll   int empNum; // Employee ID number   ofstream payFile; // Company payroll file   payFile.open(“payfile.dat”); // Open the output file   total = 0.0; // Initialize total

Payroll Program (continued)   cout << “Enter employee number: ”; // Prompt   cin >> empNum; // Read employee id no.   while (empNum != 0) // While employee   { // number isn’t zero  cout << “Enter pay rate: ”; // Prompt  cin >> payRate;         // Read hourly pay rate  cout << “Enter Hours worked: ”;  // Prompt  cin >> hours; // Read hours worked   CalcPay(payRate, hours, wages);  // Compute wages      total = total + wages; // Add wages to total      payFile << empNum << payRage // Put results in file           << hours << wages;   cout << “Enter employee number: ”;  //Prompt   cin >> empNum; // Read ID number   }   cout << “Total payroll is ” // Print total payroll        << total << endl; //  on screen   return 0; // Indicate successful } //  completion

Payroll Program (continued) //***************************************************** void CalcPay(/* in */ float payRate, // Employee’s pay rate              /* in */ float hours, // Hours worked              /* out */ float& wages) // Wages earned // CalcPay computes wages from the employee’s pay rate // and the hours worked, taking overtime into account { if (hours > MAX_HOURS; // Is there overtime?      wages = (MAX_HOURS * payRate) + // Yes                 (hours – MAX_HOURS) * payRate * OVERTIME; else      wages = hours * payRate; // No }

Always Remember and Never Forget Computers are dumb; they must be told what to do. A computer is a tool to help you solve problems. You need to apply the same strategies to solving problems using a computer as you do by hand.